The structure, distribution and function of G protein-coupled receptors are being studied. Several cDNAs for receptors expressed in brain have been cloned. The distribution of their mRNAs have bee determined by northern blots and in situ hybridization histochemistry. Expression of the receptors in mammalian cells has allowed their pharmacological properties to be characterized. Site-directed mutagenesis of the CBI cannbinoid receptor is being used to test molecular models of the receptor. Transgenic mice with either the CB1 or CB2 cannabinoid receptor knocked out are being created to study the physiological role of these receptors.